Chinese National Standard GB10631-2004 entitled “Fireworks and Firecracker—Safety and Quality”, GB 19593-2004 entitled “Fireworks and Firecracker—Combination Fireworks” and other normative references govern the requirements for combination fireworks, which are a combination of a plurality of single tube fireworks devices. Usually, the structure is formed of a plurality of rows of paper tubes, such as rectangles, cylinders, diamond shapes and fan-shaped bodies. The paper tube chamber is stuffed with propellant powder and effects, which are ignited through the fuses. The fuse structure of prior art combination fireworks are typically made as follows. Two holes are drilled in each tube wall, one is the fire entry hole into which fire enters and the other is the fire hole or fire transmission hole out of which fire exits. The fuses are divided into several short parts. The tubes are connected together by inserting the respective ends of a fuse part into the fire hole of one tube and the fire entry hole of an adjacent tube.
For example, the prior art 25-shot products comprise 5 tube rows X 5 single tubes per tube row as shown FIG. 1. The transfer order is in accordance with the fire lines 26 marked with arrows. The first tube row comprises the head-end of the paper tube series, starting with tube 11, followed in sequence by adjacent tubes 12, 13, 14 and 15. The long ignition fuse 20 is inserted into the fire entry hole (not shown) of tube 11. Tube 12 is adjacent to tube 11. The fire hole of tube 11 and fire entry hole of tube 12 are connected by inserting therein the two ends of short fuse 21. Tube 13 is adjacent to tube 12. In a similar manner, the fire hole of tube 12 and fire entry hole of tube 13 are connected by inserting therein into the two ends of short fuse 22. Tube 14 is adjacent to tube 13. The fire hole of tube 13 and fire entry hole of tube 14 are connected by inserting therein into the two ends of short fuse 23. Tube 15 is adjacent to tube 14. The fire hole of tube 14 and fire entry hole of tube 15 are connected by inserting therein into the two ends of short fuse 24.
Tube 16, which is located adjacent tube 15 is the first tube of the next row. To join the next adjacent row, the fire hole of tube 15 and fire entry hole of tube 16 are connected by inserting therein the two ends of short fuse 25, forming an inter-row fire transmission, and so on. A second long fuse (not shown) is inserted into the fire hole of tube 30, which is located at the end of the last row. The second long fuse is used as a spare ignition fuse.
In the illustrated prior art fuse structure, the fire-order is as follows: 1) ignition of fuse 20; 2) the propellant powder in tube 11 ignites short fuse 21 out of fire hole of tube 11 and into fire entry hole of tube 12; 3) the propellant powder in tube 12 ignites short fuse 22 out of fire hole of tube 12 and into fire entry hole of tube 13, and so on until the series ends.
In case there is a fault in firing, the spare ignition fuse can be ignited for a second ignition at tube 30, which is in a reverse fire transmission order. In this situation, the fire holes have the function of fire entry holes and vice versa.
There are several drawbacks to the prior art fuse structure. First, there is a lack of reliability in fire transmission and ignition. The potential of eliminating fire transmission failures is very low as the plurality of short fuses are connected but not as a singular fuse, particularly in each paper tube chamber where failures too frequently occur. Misfiring occurs once a fault has taken place at any fire transmission point, which not only leads to a firing failure affecting the fireworks display, but also may cause accidents during post-failure inspection. Second, to form a prior art fuse structure, it is necessary to cut a long fuse into multiple small parts. As the long fuse is covered by a cladding made of gunpowder, the cutting undermines the fuses lumen gunpowder distribution, and impacts the fire transmission performance. In addition, gunpowder contact is inevitable during the manual or mechanical cutting process, which is dangerous. Third, the procedure for processing traditional fuse structures is complicated and inefficient. Besides fuse cutting, punching or drilling (twice) in each tube and insertion of the short fuses are also required, and have to be done manually. During the fuse insertion process, soft and short fuses are inserted into the small holes of two adjacent tubes, which are difficult to be conducted reliably and efficiently by mechanical processes.
To overcome the problems of the prior art, an improved fuse structure for combination fireworks is needed.